1. Field of the Invention
The present invention relates to a display device having an inverted staggered thin film transistor in each of a driver circuit and a pixel portion.
2. Description of the Related Art
As one kind of field-effect transistor. a thin film transistor in which a channel formation region is formed using a semiconductor layer formed over a substrate having an insulating surface is known. Techniques in which amorphous silicon, microcrystalline silicon. or polycrystalline silicon is used for the semiconductor layer used in the thin film transistor have been disclosed. A typical application example of the thin film transistor is a liquid crystal display television device, in which the thin film transistor has been put to practical use as a switching transistor for each pixel that constitutes a display screen.
Further, there is a display device in which the number of external components is reduced and thin film transistors formed using amorphous silicon or microcrystalline silicon are used for a gate driver for reduction in cost of the display device (see Patent Document 1).